DESCRIPTION

Log::Message is a generic message storage mechanism.
It allows you to store messages on a stack -- either shared or private
-- and assign meta-data to it.
Some meta-data will automatically be added for you, like a timestamp
and a stack trace, but some can be filled in by the user, like a tag
by which to identify it or group it, and a level at which to handle
the message (for example, log it, or die with it)

Log::Message also provides a powerful way of searching through items
by regexes on messages, tags and level.

Hierarchy

There are 4 modules of interest when dealing with the Log::Message::*
modules:

Log::Message

Log::Message provides a few methods to manipulate the stack it keeps.
It has the option of keeping either a private or a public stack.
More on this below.

Log::Message::Item

These are individual message items, which are objects that contain
the user message as well as the meta-data described above.
See the Log::Message::Item manpage to see how to extract this
meta-data and how to work with the Item objects.
You should never need to create your own Item objects, but knowing
about their methods and accessors is important if you want to write
your own handlers. (See below)

Log::Message::Handlers

These are a collection of handlers that will be called for a level
that is used on a Log::Message::Item object.
For example, if a message is logged with the 'carp' level, the 'carp'
handler from Log::Message::Handlers will be called.
See the Log::Message::Handlers manpage for more explanation about how
handlers work, which one are available and how to create your own.

Log::Message::Config

Per Log::Message object, there is a configuration required that will
fill in defaults if the user did not specify arguments to override
them (like for example what tag will be set if none was provided),
Log::Message::Config handles the creation of these configurations.

As a configuration file when you create a new Log::Message object.
(The config will then only apply to that object if you marked it as
private)

As arguments when you create a new Log::Message object.

You should never need to use the Log::Message::Config module yourself,
as this is transparently done by Log::Message, but its manpage does
provide an explanation of how you can create a config file.

Options

When using Log::Message, or creating a new Log::Message object, you can
supply various options to alter its behaviour.
Of course, there are sensible defaults should you choose to omit these
options.

Below an explanation of all the options and how they work.

config

The path to a configuration file to be read.
See the manpage of Log::Message::Config for the required format

These options will be overridden by any explicit arguments passed.

private

Whether to create, by default, private or shared objects.
If you choose to create shared objects, all Log::Message objects will
use the same stack.

This means that even though every module may make its own $log object
they will still be sharing the same error stack on which they are
putting errors and from which they are retrieving.

This can be useful in big projects.

If you choose to create a private object, then the stack will of
course be private to this object, but it will still fall back to the
shared config should no private config or overriding arguments be
provided.

verbose

Log::Message makes use of another module to validate its arguments,
which is called Params::Check, which is a lightweight, yet
powerful input checker and parser. (See the Params::Check
manpage for details).

The verbose setting will control whether this module will
generate warnings if something improper is passed as input, or merely
silently returns undef, at which point Log::Message will generate a
warning.

It's best to just leave this at its default value, which is '1'

tag

The tag to add to messages if none was provided. If neither your
config, nor any specific arguments supply a tag, then Log::Message will
set it to 'NONE'

Tags are useful for searching on or grouping by. For example, you
could tag all the messages you want to go to the user as 'USER ERROR'
and all those that are only debug information with 'DEBUG'.

At the end of your program, you could then print all the ones tagged
'USER ERROR' to STDOUT, and those marked 'DEBUG' to a log file.

level

level
describes what action to take when a message is logged. Just
like tag
, Log::Message will provide a default (which is 'log') if
neither your config file, nor any explicit arguments are given to
override it.

See the Log::Message::Handlers manpage to see what handlers are
available by default and what they do, as well as to how to add your
own handlers.

remove

This indicates whether or not to automatically remove the messages
from the stack when you've retrieved them.
The default setting provided by Log::Message is '0': do not remove.

chrono

This indicates whether messages should always be fetched in
chronological order or not.
This simply means that you can choose whether, when retrieving items,
the item most recently added should be returned first, or the one that
had been added most long ago.

The default is to return the newest ones first

Methods

new

This creates a new Log::Message object; The parameters it takes are
described in the Options
section below and let it just be repeated
that you can use these options like this:

In scalar context it will return the first item matching your criteria
and in list context, it will return all of them.

If an error occurs while retrieving, a warning will be issued and
undef will be returned.

first

This is a shortcut for retrieving the first item(s) stored on the
stack. It will default to only retrieving one if called with no
arguments, and will always return results in chronological order.

If you only supply one argument, it is assumed to be the amount you
wish returned.

Furthermore, it can take the same arguments as retrieve
can.

last

This is a shortcut for retrieving the last item(s) stored on the
stack. It will default to only retrieving one if called with no
arguments, and will always return results in reverse chronological
order.

If you only supply one argument, it is assumed to be the amount you
wish returned.